Justin Long

Lem (voice)

Dwayne Johnson

Chuck Baker (voice)

Jessica Biel

Neera (voice)

Seann William Scott

Skiff (voice)

Gary Oldman

General Grawl (voice)

John Cleese

Professor Kipple (voice)

Freddie Benedict

Eckle (voice)

Alan Marriott

Glar (voice)

Mathew Horne

Soldier #1 (voice)

James Corden

Soldier #2 (voice)

Alan Cumming

Alien Mailman (voice)

Frank Welker

Ripley / Rover (voice)

Jim Cummings

Lem's Dad (voice)

Renée Zellweger

Lem's Mom (voice)

Candi Milo

Teacher (voice)

Lewis Macleod

Additional Voices (voice)

Rupert Degas

Additional Voices / Chief Gorlock (voice) (uncredited)

Rebecca Front

Additional Voices (voice)

Vincent Marzello

Additional Voices (voice)

Emma Tate

Additional Voices (voice)

Pete Atkin

Additional Voices (voice)

Laurence Bouvard

Additional Voices (voice)

Brian Bowles

Additional Voices (voice)